Styjun

I successfully set up connection from google apps script to Google Cloud firestore database with a service account. It is working fine as long I store the credentials in the apps script file itself. If I store the private Key of the credential somewhere else (in database, in a drive file, google doc...) oauth2 authentication fails with error: "Invalid Argument: Key" thrown by GAS Oauth2 library.

I investigated further and it seems an encoding/charset problem. If I compare the length of the private Key string between hard coded and stored in a File/DB the length of the key is not equal, but the key-strings seems to be identical.

Some help would be appreciated.

function createOAuth() 

// credentials of service account hard coded 
var jsonObj = 
 "type": "service_account",
 "project_id": "id of project",
 "private_key": "-----BEGIN PRIVATE KEY-----.....----END PRIVATE KEY-n",
 "client_email": "servic accoutn email",
 "auth_uri": "https://accounts.google.com/o/oauth2/auth",
 "token_uri": "https://oauth2.googleapis.com/token", 
 

// not working if store attribute private_key somewhere else like:
/*var fileContent = DriveApp.getFileById('idOfFile').getBlob().getDataAsString("UTF-8"); //OR
DocumentApp.getBody().getText() //OR
var privateKey = Utilities.newBlob(privatKeyFromCredents).getDataAsString()
//store key in cloud firestore database also not working. 
*/

return OAuth2.createService("Service Account")
 .setTokenUrl('https://accounts.google.com/o/oauth2/token')
 .setPrivateKey(jsonObj.private_key)
 .setIssuer(jsonObj.client_email)
 .setPropertyStore(PropertiesService.getScriptProperties())
 .setCache(CacheService.getScriptCache())
 .setParam('access_type', 'offline')
 .setScope('https://www.googleapis.com/auth/script.external_request https://www.googleapis.com/auth/cloud-platform https://www.googleapis.com/auth/datastore');

var access = service.hasAccess(); // true if jsonObj is hard coded 
// false if stored somewhere else --> error: Invalid Argument: Key
Logger.log('Access: ' + access); 

// get Credentials form Drive in JSON format
var fileContent = DriveApp.getFileById('18t9NnzwKMlmQAnRUa_KovWdDvhk60oZT').getBlob().getDataAsString("UTF-8");

var serviceCredentials = JSON.parse(fileContent);
serviceCredentials['service_name'] = "Service Account Name";
serviceCredentials['scope'] = "https://www.googleapis.com/auth/script.external_request https://www.googleapis.com/auth/cloud-platform https://www.googleapis.com/auth/datastore ";

var service = OAuth2.createService(serviceCredentials.service_name)
.setTokenUrl(serviceCredentials.token_uri)
.setPrivateKey(serviceCredentials.private_key)
.setIssuer(serviceCredentials.client_email)
.setPropertyStore(PropertiesService.getUserProperties())
.setCache(CacheService.getUserCache())
.setParam('access_type', 'offline')
.setScope(serviceCredentials.scope);

// for testing if access oauth setup is working or not
var access = service.hasAccess();
Logger.log('Access: ' + access); //true or false